diff --git a/tests/core/serialize/CMakeLists.txt b/tests/core/serialize/CMakeLists.txt
index 13ce3eae..dec91467 100644
--- a/tests/core/serialize/CMakeLists.txt
+++ b/tests/core/serialize/CMakeLists.txt
@@ -30,8 +30,6 @@ set(test_files
     ForUpdate.cpp
     From.cpp
     Insert.cpp
-    IsNotNull.cpp
-    IsNull.cpp
     Lower.cpp
     Parameter.cpp
     ParameterizedVerbatim.cpp
diff --git a/tests/core/serialize/IsNotNull.cpp b/tests/core/serialize/IsNotNull.cpp
deleted file mode 100644
index 695e0f6c..00000000
--- a/tests/core/serialize/IsNotNull.cpp
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
- * Copyright (c) 2023, Roland Bock
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification,
- * are permitted provided that the following conditions are met:
- *
- *  * Redistributions of source code must retain the above copyright notice,
- *    this list of conditions and the following disclaimer.
- *  * Redistributions in binary form must reproduce the above copyright notice,
- *    this list of conditions and the following disclaimer in the documentation
- *    and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
- * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
- * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
- * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
- * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
- * OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include "Sample.h"
-#include "compare.h"
-#include <sqlpp11/sqlpp11.h>
-
-int IsNotNull(int, char* [])
-{
-  const auto bar = test::TabBar{};
-
-  // Single column.
-  SQLPP_COMPARE(is_not_null(bar.textN), "(tab_bar.text_n IS NOT NULL)");
-
-  // Expression.
-  SQLPP_COMPARE(is_not_null(bar.textN + "suffix"), "((tab_bar.text_n || 'suffix') IS NOT NULL)");
-
-  // With sub select.
-  SQLPP_COMPARE(is_not_null(select(sqlpp::value("something").as(sqlpp::alias::a))), "((SELECT 'something' AS a) IS NOT NULL)");
-
-  // Requires parens.
-  SQLPP_COMPARE(is_not_null(bar.textN) or bar.textN == "", "((tab_bar.text_n IS NOT NULL) OR (tab_bar.text_n = ''))");
-  SQLPP_COMPARE(bar.textN == "" or is_not_null(bar.textN), "((tab_bar.text_n = '') OR (tab_bar.text_n IS NOT NULL))");
-
-  return 0;
-}
diff --git a/tests/core/serialize/IsNull.cpp b/tests/core/serialize/IsNull.cpp
deleted file mode 100644
index e5e5102f..00000000
--- a/tests/core/serialize/IsNull.cpp
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
- * Copyright (c) 2023, Roland Bock
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification,
- * are permitted provided that the following conditions are met:
- *
- *  * Redistributions of source code must retain the above copyright notice,
- *    this list of conditions and the following disclaimer.
- *  * Redistributions in binary form must reproduce the above copyright notice,
- *    this list of conditions and the following disclaimer in the documentation
- *    and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
- * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
- * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
- * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
- * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
- * OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include "Sample.h"
-#include "compare.h"
-#include <sqlpp11/sqlpp11.h>
-
-int IsNull(int, char* [])
-{
-  const auto bar = test::TabBar{};
-
-  // Single column.
-  SQLPP_COMPARE(is_null(bar.textN), "(tab_bar.text_n IS NULL)");
-
-  // Expression.
-  SQLPP_COMPARE(is_null(bar.textN + "suffix"), "((tab_bar.text_n || 'suffix') IS NULL)");
-
-  // With sub select.
-  SQLPP_COMPARE(is_null(select(sqlpp::value("something").as(sqlpp::alias::a))), "((SELECT 'something' AS a) IS NULL)");
-
-  // Requires parens.
-  SQLPP_COMPARE(is_null(bar.textN) or bar.textN == "", "((tab_bar.text_n IS NULL) OR (tab_bar.text_n = ''))");
-  SQLPP_COMPARE(bar.textN == "" or is_null(bar.textN), "((tab_bar.text_n = '') OR (tab_bar.text_n IS NULL))");
-
-  return 0;
-}